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| author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-06-08 21:20:41 +0400 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-06-10 11:37:25 +0200 |
| commit | 16882c1e962b4be5122fc05aaf2afc10fd9e2d15 (patch) | |
| tree | c39cae4ae4874998d7e3486cd57d57613b05a89c /kernel | |
| parent | 39b945a37bac2b692773a470890c8ba301485b15 (diff) | |
| download | linux-16882c1e962b4be5122fc05aaf2afc10fd9e2d15.tar.gz linux-16882c1e962b4be5122fc05aaf2afc10fd9e2d15.tar.bz2 linux-16882c1e962b4be5122fc05aaf2afc10fd9e2d15.zip | |
sched: fix TASK_WAKEKILL vs SIGKILL race
schedule() has the special "TASK_INTERRUPTIBLE && signal_pending()" case,
this allows us to do
current->state = TASK_INTERRUPTIBLE;
schedule();
without fear to sleep with pending signal.
However, the code like
current->state = TASK_KILLABLE;
schedule();
is not right, schedule() doesn't take TASK_WAKEKILL into account. This means
that mutex_lock_killable(), wait_for_completion_killable(), down_killable(),
schedule_timeout_killable() can miss SIGKILL (and btw the second SIGKILL has
no effect).
Introduce the new helper, signal_pending_state(), and change schedule() to
use it. Hopefully it will have more users, that is why the task's state is
passed separately.
Note this "__TASK_STOPPED | __TASK_TRACED" check in signal_pending_state().
This is needed to preserve the current behaviour (ptrace_notify). I hope
this check will be removed soon, but this (afaics good) change needs the
separate discussion.
The fast path is "(state & (INTERRUPTIBLE | WAKEKILL)) + signal_pending(p)",
basically the same that schedule() does now. However, this patch of course
bloats schedule().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index bfb8ad8ed171..2c65bf29d133 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4159,12 +4159,10 @@ need_resched_nonpreemptible: clear_tsk_need_resched(prev); if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { - if (unlikely((prev->state & TASK_INTERRUPTIBLE) && - signal_pending(prev))) { + if (unlikely(signal_pending_state(prev->state, prev))) prev->state = TASK_RUNNING; - } else { + else deactivate_task(rq, prev, 1); - } switch_count = &prev->nvcsw; } |